The clinical anatomy of the insertion of the rotator cuff tendons.

The rotator cuff (RC) insertions according to most anatomical texts are described as being separate from one another. However, clear fusion of the RC tendon fibres exists with prior studies showing this interdigitation forming a common, continuous insertion onto and around the lesser and greater tubercles (LT and GT) of the humerus. Current surgical repair methods (especially arthroscopic techniques) rarely mention or consider these connections during repair and suture anchor implantation. The general principles of RC surgery remain a controversial subject, due to various available techniques, surgeon experience and preference, and the contradicting success rates. This results from old-fashioned knowledge of the anatomy of the RC complex and its functional aspects. Therefore, the purpose of this project was to visualise and define the RC footprint and extension insertions with the aim of enhancing and improving knowledge of the basic anatomy in the hopes that this will be considered during orthopaedic repair. Twenty shoulders (16 cadaveric and 4 fresh) were used in the study. The fresh shoulders were received from the National Tissue Bank, and ethical clearance was obtained (239/2015). Reverse dissection was performed to better visualise the RC unit exposing the interdigitated rotator hood (extension insertions), as well as the complete RC unit (tendons + internal capsule) separated from the scapula and humerus. Once the insertions were exposed and documented, the RC muscle footprint (articular surface area) was measured and recorded, using AutoCAD 2016. No statistical significant difference between left and right (p = 0.424) was noted, but a significant difference between males and females (p = 0.000) was. Collectively, these findings indicate and strengthen evidence towards the notion that the RC muscles/tendons and the internal capsule are one complete and inseparable unit/complex. The fact that the RC unit is more complex in its structure and attachment places importance on the biomechanical stresses encountered after repair. Functions of one RC muscle are not necessarily isolated but instead can be influenced by surrounding muscles as well. In addition to providing greater understanding of the basic anatomy of the RC unit, these findings also provide clarity for surgeons with the goal of improving and enhancing surgical methods for better post-operative patient outcome.